WO 01/64277 A2 discloses a device for the detection of vulnerable plaque within an artery. The device includes an elongate shaft having a distal end and a proximal end. A detector assembly is fixed to the elongate shaft proximate the distal end thereof. In one example, the detector assembly 726 includes a substrate 742 and a cover 744 that define a sensor array chamber 746. The cover 744 is sealingly fixed to substrate 742 by a bond 748. A plurality of pixels 751 are disposed on a top surface of substrate 742 of detector assembly 726 to obtain a thermal image of a strip of plaque and nearby vessel wall. Each pixel comprises a sensing element 752 and a cavity 750 defined by substrate 742.
Due to the sealingly fixation of the cover to the substrate by a bond, such detector assembly cannot be realized in small dimensions. Further, such bonding is not easy and expensive and in particular not suitable for mass manufacturing.
U.S. Pat. No. 6,262,417 B1 discloses an infrared bolometer including an active matrix level having a substrate and a pair of connecting terminals, a support level provided with a pair of bridges and a pair of conduction lines, an absorption level including a bolometer element surrounded by an absorber and a pair of posts positioned between the support level and the absorption level. Each of the bridges is provided with an anchor portion, a leg portion and an elevated portion, the anchor portion being affixed to the active matrix level and the elevated portion being apart from the active matrix level, wherein the elevated portion of each of the bridges including an inner part cantilevered from an outer part. Each of the posts includes an electrical conduit, wherein each ends of the bolometer element is electrically connected to the respective connecting terminal through the respective conduit and the respective conduction line.
A similar device is also disclosed in “Design and fabrication of a high fill-factor micro-bolometer using double sacrificial layers”, Ju et al., SPIE Vol. 3698 Infrared Technology and Applications XXV (1999). The fabrication of this bolometer features that it uses double sacrificial layers so as to separate the absorber level from the bridge structure, electrical and thermal path between the absorber and substrate.
As the bolometric element is located in the upper membrane, such bolometer can suffer from a high thermal loss to the ambient air and/or can be fragile.